Method and Apparatus for Resource Aggregation in Wireless Communications

ABSTRACT

Methods and apparatus for cell aggregation are disclosed. In accordance with one aspect information regarding a predefined maximum number of cells that can be aggregated by a communication device on a single carrier resource is sent by the communication device. Said Information is received by a network node where after control on cell aggregation can be based on the information, and the communication device can support cell aggregation on the single carrier resource up to said maximum number of cells.

The application relates to resource aggregation in wirelesscommunications and more particularly to single carrier resourceaggregation in a communication system.

A communication system can be seen as a facility that enablescommunication sessions between two or more nodes such as fixed or mobilecommunication devices, access nodes such as base stations, servers andso on. A communication system and compatible communicating entitiestypically operate in accordance with a given standard or specificationwhich sets out what the various entities associated with the system arepermitted to do and how that should be achieved. For example, thestandards, specifications and related protocols can define the mannerhow communication devices shall communicate with the access nodes, howvarious aspects of the communications shall be implemented and how thedevices shall be configured.

A communication can be carried on wired or wireless carriers. Examplesof wireless systems include public land mobile networks (PLMN) such ascellular networks, satellite based communication systems and differentwireless local networks, for example wireless local area networks(WLAN). Wireless systems can be divided into coverage areas referred toas cells, such systems being often referred to as cellular systems. Anexample of cellular communication systems is an architecture that isbeing standardized by the 3rd Generation Partnership Project (3GPP).This system is often referred to as the long-term evolution (LTE) of theUniversal Mobile Telecommunications System (UMTS) radio-accesstechnology. A further development of the LTE is often referred to asLTE-Advanced. The various development stages of the 3GPP LTEspecifications are referred to as releases.

Radio services areas are typically referred to as cells. A cell can beprovided by a base station, there being various different types of basestations. Different types of cells can provide different features. Forexample, cells can have different shapes, sizes and othercharacteristics.

A user can access the communication system by means of an appropriatecommunication device. A communication device of a user is often referredto as user equipment (UE) or terminal. A communication device isprovided with an appropriate signal receiving and transmittingarrangement for enabling communications with other parties. Typically acommunication device is used for enabling receiving and transmission ofcommunications such as speech and data. In wireless systems acommunication device provides a transceiver station that can communicatewith another communication device such as e.g. a base station of anaccess network and/or another user equipment. The communication devicemay access a carrier provided by a base station, and transmit and/orreceive communications on the carrier.

Carrier aggregation (CA) can be used to increase performance. In carrieraggregation a plurality of component carriers on different frequenciesare aggregated to increase bandwidth. In accordance with LTE Release 10user equipment carrier aggregation (UE CA) capability integrates allcarrier aggregation (CA) features in a capability set. In LTE release 10UE CA capability has been comprehensively defined and includes featuressuch as those related to UE radio frequency (RF) properties,decoding/encoding, hybrid automatic repeat request (HARQ) signallingsupport, blind decoding, the secondary serving cell (SCC) management,dual-Component Carrier capability, capability to monitor physicaldownlink control channel (PDCCH) on multiple cells, and so on. In otherwords, if a user equipment supports carrier aggregation (CA), it shallsupport all CA related features. Such a user equipment is necessarily adual component carrier capable user equipment operable on multiplefrequency resources. However, a user equipment that is capable only forcommunications on a single frequency carrier at a time cannot beconfigured to support the required dual component carrier aggregationrelated features and thus cannot provide any aggregation. On the otherhand, single frequency communication devices may be desired in certainoccasions, for example due to the lesser complexity and cost thereof.

According to an aspect, there is provided an apparatus for acommunication device, the apparatus comprising at least one processor,and at least one memory including computer program code, wherein the atleast one memory and the computer program code are configured, with theat least one processor, to support cell aggregation for communicationswith a multiple of cells of a communication system based on a predefinedmaximum number of cells on a single carrier resource that can beaggregated by the communication device.

According to another aspect there is provided an apparatus forcontrolling cell aggregation, the apparatus comprising at least oneprocessor, and at least one memory including computer program code,wherein the at least one memory and the computer program code areconfigured, with the at least one processor, to receive from acommunication device information of a predefined maximum number of cellsthe communication device supports for cell aggregation on a singlecarrier resource, and to control cell aggregation by the communicationdevice based on the information.

According to another aspect there is provided a method for cellaggregation, comprising signalling information regarding a predefinedmaximum number of cells that can be aggregated by a communication deviceon a single carrier resource, and supporting cell aggregation forcommunications by the communication device on the single carrierresource with a multiple of cells up to said maximum number of cells.

According to another aspect there is provided a method for controllingcell aggregation, comprising receiving information of a predefinedmaximum number of cells a communication device supports for cellaggregation on a single carrier resource, and controlling cellaggregation on the single carrier resource by the communication devicebased on the information.

According to a yet another aspect there is provided a method andapparatus for communications on a system where cell aggregation isavailable, wherein single frequency resource aggregation is provided forcommunications by a first communication device configured with a subsetof capabilities selected from a set of capabilities defined for acommunication device capable of component carrier communication onmultiple frequency resources, and single frequency resource aggregationfor is provided communications by at least one second communicationdevice configured with a different subset of capabilities selected fromsaid set of capabilities defined for a communication device capable ofcomponent carrier communication on multiple frequency resources.

In accordance with a more detailed embodiment an indication of themaximum number of cells is signalled from the communication device. Thesignalling can be explicit or implicit. The indication may be signalledin capability information of the communication device.

The maximum number of cells may be defined by means of a capabilityinformation parameter.

The communication device may be configured for simultaneous transmissionto and/or reception from multiple cells on the single carrier resource.According to an embodiment the communication device is configured toseparate transmission and/or reception on the single carrier resourcebased on time division multiplexing.

The single carrier resource may comprise a single frequency carrier.

The predefined maximum number of cells may define the maximum number ofphysical shared channels and/or physical control channels that can bereceived or transmitted by the communication device.

The apparatus may be configured to monitor for an identity at a time ina search space up to the predefined maximum number of cells.Alternatively, simultaneous monitoring of a plurality of identities in asearch space up to the predefined maximum number of cells may beprovided.

Single frequency resource communications with multiple cells can beprovided based on a set of capabilities selected from a set ofcapabilities for communications on a multi-frequency component carrier.

Information of the predefined maximum number of cells may be signalledin response to a request for capability information.

Signalling for controlling the cell aggregation may be provided from acell or from a plurality of cells depending on the capability categoryof the communication device.

One of the cells may grant a physical downlink shared channel providedby any of the multiple of cells.

Downlink assignments may be provided either with or without a cellindicator depending on the capability category of the communicationdevice.

Power control may be provided on a serving cell basis.

A node such as a base station or a mobile station can be configured tooperate in accordance with the various embodiments.

A computer program comprising program code means adapted to perform themethod may also be provided.

It should be appreciated that any feature of any aspect may be combinedwith any other feature of any other aspect.

Embodiments will now be described in further detail, by way of exampleonly, with reference to the following examples and accompanyingdrawings, in which:

FIG. 1 shows a schematic diagram of a network according to someembodiments;

FIG. 2 shows a schematic diagram of a mobile communication deviceaccording to some embodiments;

FIG. 3 shows a schematic diagram of a control apparatus according tosome embodiments; and

FIGS. 4 and 5 show schematically flowcharts according to certainembodiments.

In the following certain exemplifying embodiments are explained withreference to a wireless or mobile communication system serving mobilecommunication devices. Before explaining in detail the exemplifyingembodiments, certain general principles of a wireless communicationsystem, access systems thereof, and mobile communication devices arebriefly explained with reference to FIGS. 1 to 3 to assist inunderstanding the technology underlying the described examples.

A non-limiting example of the recent developments in communicationsystem architectures is the long-term evolution (LTE) of the UniversalMobile Telecommunications System (UMTS) that is being standardized bythe 3rd Generation Partnership Project (3GPP). As explained above,further development of the LTE is referred to as LTE-Advanced. The LTEemploys a mobile architecture known as the Evolved Universal TerrestrialRadio Access Network (E-UTRAN). Base stations of such systems are knownas evolved or enhanced Node Bs (eNBs) and may provide E-UTRAN featuressuch as user plane Radio Link Control/Medium Access Control/Physicallayer protocol (RLC/MAC/PHY) and control plane Radio Resource Control(RRC) protocol terminations towards the communication devices. Otherexamples of radio access system include those provided by base stationsof systems that are based on technologies such as wireless local areanetwork (WLAN) and/or WiMax (Worldwide Interoperability for MicrowaveAccess).

A communication device 101, 102, 103 is typically provided wirelessaccess via at least one base station or similar wireless transmitterand/or receiver node of an access system. In FIG. 1 differentneighbouring and/or overlapping access systems or radio service areas100, 110, 117 and 119 are shown being provided by base stations 105,106, 118 and 119. It is noted that instead of four access systems, anynumber of access systems can be provided in a communication system. Anaccess system can be provided by a cell of a cellular system andtherefore the access system will be referred to hereinafter as cells. Itis noted that the cell borders are schematically shown for illustrationpurposes only in FIG. 1. It shall be understood that the sizes andshapes of the cells or other radio service areas may vary considerablyfrom the similarly sized omni-directional shapes of FIG. 1.

A base station site can provide one or more cells or sectors, eachsector providing a cell or a subarea of a cell. A radio link within acell can be identified by a single logical identification. Eachcommunication device and base station may have one or more radiochannels open at the same time and may send signals to and/or receivesignals from more than one source

Base stations are typically controlled by at least one appropriatecontroller apparatus so as to enable operation thereof and management ofmobile communication devices in communication with the base stations.FIG. 1 shows control apparatus 107 and 109. The control apparatus can beinterconnected with other control entities. The control apparatus cantypically be provided with memory capacity and at least one dataprocessor. The control apparatus and functions may be distributedbetween a plurality of control units. In some embodiments, each basestation can comprise a control apparatus. In alternative embodiments,two or more base stations may share a control apparatus. Currently LTEdoes not have a separate radio network controller. In some embodimentsthe control apparatus may be respectively provided in each base station.

Different types of possible cells include those known as macro cells,pico cells and femto cells. For example, in LTE-Advanced thetransmission/reception points or base stations can comprise wide areanetwork nodes such as a macro eNode B (eNB) which may, for example,provide coverage for an entire cell or similar radio service area. Basestation can also be provided by small or local radio service areanetwork nodes, for example Home eNBs (HeNB), pico eNodeBs (pico-eNB), orfemto nodes. Some applications utilise radio remote heads (RRH) that areconnected to for example an eNB. Cell areas typically overlap, and thusa communication device in an area can listen to more than one basestation. Smaller radio service areas can be located entirely or at leastpartially within a larger radio service area. A communication may thuscommunicate with more than one cell. In some embodiments LTE-Advancednetwork nodes can comprise a combination of wide area network nodes andsmall area network nodes deployed using the same frequency carriers(e.g. co-channel deployment).

In particular, FIG. 1 depicts a first cell 100. In this example thefirst cell 100 is provided by a wide area base station 106, which can bea macro-eNB. The macro-eNB 106 transmits and receives data over theentire coverage of the cell 100. A second cell 110 in this example is apico-cell. A third cell 117 is provided by a suitable small area networknode 118 such as Home eNBs (HeNB) (femto cell) or another pico eNodeBs(pico-eNB). HeNBs may be configured to support local offload and maysupport any user equipment (UE) or UEs belonging to a closed subscribergroup (CSG) or an open subscriber group (OSG) and transmit and receivedata over the coverage area of the third cell 117. A fourth cell 119 isprovided by a remote radio head (RRH) 120 connected to the base stationapparatus of cell 100.

One technique of communicating over a wireless interface relies oncombining the results of detecting a transmission from a communicationsdevice at a plurality of cells or detecting a transmission based onsignals transmitted from a plurality of cells. This is commonly known ascoordinated multipoint transmission (CoMP). CoMP can be provided forexample in heterogeneous network scenarios where there is a centralisedprocessing unit, for example where there is a single controlling macroeNB.

In FIG. 1 stations 106 and 107 are shown as connected to a widercommunications network 113 via gateway 112. A further gateway functionmay be provided to connect to another network. The smaller stations 118and 120 can also be connected to the network 113, for example by aseparate gateway function and/or via the macro level cells. In theexample, station 118 is connected via a gateway 111 whilst station 120connects via the controller apparatus 108. Base station may communicatevia each other via fixed line connection and/or air interface, forexample over an X2 interface.

As shown, each of the communication devices 101, 102 and 103 is locatedwithin the area of at least two cells, and can thus be in simultaneouscommunications with more than one cell. For example, all of thecommunication devices are within the service area of the macro cell basestation 106 and its associated controller 109 which is further coupledto the pico cell base station controller 109 and to the femto cellgateway 111. The macro cell base station 106 is configured tocommunicate to communication devices operating within the range of themacro cell in such a way that the downlink is able to transmit controland signal information from the macro cell base station antenna to thecommunication devices. Similarly, communication devices 102 and 103 maybe configured to transmit via an uplink to the pico cell base station107 and also in some embodiments transmit at least control informationvia a control channel to the macro cell base station 106. Communicationdevice 103 may also communicate with at least one of cells 117 and 119.

A possible mobile communication device for transmitting to and receivingfrom a plurality of base stations will now be described in more detailwith reference to FIG. 2 showing a schematic, partially sectioned viewof a communication device 200. Such a communication device is oftenreferred to as user equipment (UE) or terminal. An appropriate mobilecommunication device may be provided by any device capable of sendingradio signals to and/or receiving radio signals from multiple cells.Non-limiting examples include a mobile station (MS) such as a mobilephone or what is known as a ‘smart phone’, a portable computer providedwith a wireless interface card or other wireless interface facility,personal data assistant (ETA) provided with wireless communicationcapabilities, or any combinations of these or the like. A mobilecommunication device may provide, for example, communication of data forcarrying communications such as voice, electronic mail (email), textmessage, multimedia and so on. Users may thus be offered and providednumerous services via their communication devices. Non-limiting examplesof these services include two-way or multi-way calls, data communicationor multimedia services or simply an access to a data communicationsnetwork system, such as the Internet. User may also be providedbroadcast or multicast data. Non-limiting examples of the contentinclude downloads, television and radio programs, videos,advertisements, various alerts and other information.

The mobile device may receive signals over an air interface 207 viaappropriate apparatus for receiving and may transmit signals viaappropriate apparatus for transmitting radio signals. In FIG. 2transceiver apparatus is designated schematically by block 206. Thetransceiver apparatus 206 may be provided for example by means of aradio part and associated antenna arrangement. The antenna arrangementmay be arranged internally or externally to the mobile device.

A mobile communication device is also provided with at least one dataprocessing entity 201, at least one memory 202 and other possiblecomponents 203 for use in software and hardware aided execution of tasksit is designed to perform, including control of access to andcommunications with access systems and other communication devices. Thedata processing, storage and other relevant control apparatus can beprovided on an appropriate circuit board and/or in chipsets. Thisfeature is denoted by reference 204.

The user may control the operation of the mobile device by means of asuitable user interface such as keypad 205, voice commands, touchsensitive screen or pad, combinations thereof or the like. A display208, a speaker and a microphone can be also provided. Furthermore, amobile communication device may comprise appropriate connectors (eitherwired or wireless) to other devices and/or for connecting externalaccessories, for example hands-free equipment, thereto.

FIG. 3 shows an example of a control apparatus for a communicationsystem, for example to be coupled to and/or for controlling a station ofan access system. In some embodiments base stations comprise a separatecontrol apparatus. In other embodiments the control apparatus can beanother network element. The control apparatus 300 can be arranged toprovide control on communications in the service area of the system. Thecontrol apparatus 300 can be configured to provide control functions inassociation with cell aggregation on a single carrier resource by meansof the data processing facility in accordance with certain embodimentsdescribed below. For this purpose the control apparatus comprises atleast one memory 301, at least one data processing unit 302, 303 and aninput/output interface 304. Via the interface the control apparatus canbe coupled to a receiver and a transmitter of the base station. Thecontrol apparatus can be configured to execute an appropriate softwarecode to provide the control functions. It shall be appreciated thatsimilar component can be provided in a control apparatus providedelsewhere in the system for controlling reception of sufficientinformation for decoding of received information blocks.

A wireless communication device, such as a mobile or base station, canbe provided with a Multiple Input/Multiple Output (MIMO) antenna system.MIMO arrangements as such are known. MIMO systems use multiple antennasat the transmitter and receiver along with advanced digital signalprocessing to improve link quality and capacity. The transceiverapparatus 206 of FIG. 2 can provide a plurality of antenna ports. Moredata can be received and/or sent where there are more antennae elements.

The following describes certain exemplifying embodiments where cellaggregation is provided for communication by a communication device.Cell aggregation can be understood as an intra-frequency inter-sitecombination, a difference to carrier aggregation being that carrieraggregation is provided over multiple frequencies whereas cellaggregation can be provided on a single carrier resource, such as on asingle frequency band. Therefore cell aggregation requires differentcapability from the communication device to that of carrier aggregation.For example, a cell aggregation capable radio only needs to support onefrequency.

FIG. 4 shows an example for operation at a communication device that iscapable for cell aggregation. At step 40 the communication device maydetermine if cell aggregation would provide any benefit, or if it iseven possible. At 42 the communication device can then signalinformation regarding a predefined maximum number of cells that can beaggregated by a communication device on a single carrier resource. Basedon this information the network can control the communicationaccordingly and assign appropriate resources, where after support can beprovided at 44 for cell aggregation for communications by thecommunication device on the single carrier resource with a multiple ofcells up to said maximum number of cells.

FIG. 5 illustrates an example of how to control the cell aggregation atthe network side. When a new communication device enters a cell,capability information may be requested from it at 50. Information of apredefined maximum number of cells the communication device supports forcell aggregation on a single carrier resource can be received at 52 as apart of the requested capability information. Cell aggregation on thesingle carrier resource by the communication device can then becontrolled based on the received information. For example, the relevantnetwork controller can assign communication channels and other resourcesat 54 up to the maximum number of cells and provide appropriate controlfor the communications on the single carrier resource at 56.

The following more detailed embodiments describe cell aggregationcapability categories of a communication device with reference to acommunication device provided by a LTE enabled a user equipment (UE). Inthe described user equipment categories only features that are needed tosupport single frequency cell aggregation are provided, with varyingdegree of sophistication. As discussed above, dual component carrieruser equipments, i.e. user equipments that can communicate on multiplefrequencies, can get benefit from carrier aggregation and also from cellaggregation. However, single frequency carrier user equipments are notprovided with all of the required essential features of the carrieraggregation capability set, as defined e.g. by LTE release 10. Theinventors have found that single frequency cell aggregation does noteven require all of the UE capabilities that are defined formulti-frequency carrier aggregation (CA) in LTE Release 10 and that onlya sub-set of the carrier aggregation capabilities would be required insupport of cell aggregation. Such devices are nevertheless preventedfrom using cell aggregation due to the lacking features.

In accordance with certain embodiments reduced user equipment (UE)capability sets are defined for a user equipment for use in cellaggregation. In accordance with an embodiment UE CA features defined inLTE Release 10 are arranged in subgroups such that one or multiple newUE capability classes or sets can be provided for single frequency cellaggregation. In each capability class only a subset of LTE Release 10carrier aggregation (CA) features is supported. Thus a plurality ofdifferent user equipment categories or types can be provided, each ofthe types and related behaviours supporting multiple serving cells on asingle carrier resource. For example, monitoring of temporaryidentifiers assigned for the user equipment by the access system can behandled differently, depending on the capability set configuration.Also, granting of physical shared channels and communications onphysical shared channels (e.g. PDSCH, PUSCH) can be handled differentlydepending on the configured capabilities. Further examples wheredifferent configurations may be provided depending on the capability setrelate to downlink assignments and power control.

The categorization of user equipment capabilities based on the existingcarrier aggregation framework enables production of several differentcell aggregation user equipment capability groups and user equipmentswith different level of complexity and cost. Thus cell aggregation maybe supported at an optimised complexity and cost, depending on the needsof users. Use of the existing features as a starting point may alsoprovide advantage in that a minimal amount of standardization isrequired since existing carrier aggregation features may be reused.

Simultaneous or non-simultaneous downlink (DL) reception and/or uplink(UL) transmissions can be supported depending on the capability class.The non-simultaneous communications can be separated by means of timedivision multiplexing (TDM).

In accordance with an embodiment a parameter for cell aggregationcapability can be signalled from the user equipment in user equipment(UE) capability signalling for indication of the number of downlink (DL)same frequency cells which the user equipment can aggregate. Forexample, a base station can ask from the UE for its capabilityinformation and the UE can signal the capability information with anindication of its cell aggregation capabilities back to the basestation. Signalling of the cell aggregation capability information canbe explicit or implicit. For simplicity, a parameter indicating themaximum number of supported cells is denoted in the following as M.

It is noted that even if the user equipment supports cell aggregationfeature up to M cells, the arrangement can be such that it only usescell aggregation when radio conditions are such that use of cellaggregation is beneficial. For example, if the user equipment can onlydetect one cell there is no need for it even to try to connect to morecells.

The parameter M can be defined by the vendor of the user equipment, forexample based on a standardised framework of user equipment categories.High M value can mean relatively high requirements from the userequipment implementation. For example, baseband processing, signallingsupport, measurement capability, and so forth are required. This alsomeans increased complexity and higher cost of user equipment chipset,and thus would most likely be used for high-end user equipments. A lowerM would in this scenario mean less complex and thus easierimplementation, thus resulting a lower cost user equipment.

Various possible user equipment cell aggregation capability categoriescan be provided based on the features of a multi-frequency capabilityset, such as the LTE Release 10 capability set discussed above.Non-limiting examples of possible capability sets are referred below ascell aggregation capability sets 1 to 5.

Cell aggregation Capability set 1 provides for downlink (DL) cross cellscheduling. Based on this set an user equipment is capable ofsupporting:

-   1. A physical downlink control channel (PDCCH) monitoring for a Cell    Radio Network Temporary identity (C-RNTI) on a user equipment    specific search space for one Serving Cell. Up to M PDCCHs can be    provided in one user equipment specific search space per user    equipment. The channels are provided non-simultaneously.-   2. Physical Downlink Shared Channel (PDSCH) reception on up to M    Serving Cells on same frequency. The reception is non-simultaneous.-   3. DL assignments with cell indicator (Carrier or Cell Indicator    Field) CIF for CA cross scheduling can be reused, and thus no new    LTE Downlink Control Information (DCI) formats need to be defined.

Cell aggregation Capability set 2 for DL cell aggregation. Based on thisset an user equipment (UE) is capable of:

-   1. PDCCH monitoring for C-RNTI on user equipment specific search    space on M Serving Cells.-   2. PDSCH reception on up to M Serving Cells on same frequency.-   3. DL assignments without cell indicator (CIF bits in accordance    with LTE Release 10 Downlink Control Information; DCI)

Cell aggregation Capability set 3 for advanced DL cell aggregation. Thisset is a combination of capability sets 1 and 2 above. Based on this setuser equipment capabilities are:

-   1. PDCCH monitoring for C-RNTI on user equipment specific search    space on M Serving Cells.-   2. PDCCH monitoring for C-RNTI on multiple UE specific search spaces    on one serving Cell.-   3. PDSCH from any cell can only be granted by PDCCH in one cell.-   4. PDSCH reception, on up to M Serving Cells on same frequency.-   5. DL assignments with cell indicator

Cell aggregation Capability set 4 for UL cell aggregation. This setrequires cell aggregation capability of set 1, 2 or 3. User equipmentconfigured in accordance with this set is capable of:

-   1. PUSCH transmission on up to M Serving Cells on same frequency.    The transmissions are not simultaneous.-   2. Physical Hybrid ARQ Indicator Channel (PHICH) reception for PUSCH    transmissions on up to M serving cells (SCells).-   3. Periodic Sounding Reference Symbols (SRS) transmission on M    Serving Cells, as per RRC configuration on same frequency, not    simultaneous.-   4. Power control on a per Serving Cell basis

According to a possibility a fifth cell aggregation capability set canbe provided by adding UL grants with cell indicator to capability set 4.

The above capability sets highlight the features that differentiatebetween the different capability categories 1 to 5. Naturally, the listsare not exhaustive and other features of a control channel may beprovided in practise. The other features can also be based on the fullcarrier aggregation (CA) capability set. For example, feedback mechanismsuch as Ack/Nak on Physical Uplink Shared Channel (PUSCH)/PhysicalUplink Control Channel (PUCCH) and/or Channel QualityIndicator/Precoding Matrix Index/Rank Indicator (CQI/PMI/RI)periodical/aperiodical feedback may be added. A more detailed example ofthe further features is described below where a set of possible cellaggregation capability requirements is given in relation to the aboveaggregation capability set 1:

-   1) PDCCH monitoring for C-RNTI on UE specific search space for one    Serving Cell (S-Cell). Up to M PDCCH in one UE specific search space    per UE can be monitored. The monitoring is provided    non-simultaneously.-   2) PDSCH reception, on up to M Serving Cells on same frequency,    non-simultaneously.-   3) DL assignments with cell indicator (CIF for CA cross scheduling    can be reused, and thus no new DCI format needs to be defined)-   4) PDSCH starting position determination by decoding of Physical    Control Format Indicator Channel (PCFICH), on N Serving Cells.-   5) Error correction Ack/Nack feedback, for up to N Serving Cells    altogether on:    -   PUSCH    -   PUCCH format 1b with channel selection        -   for FDD and TDD using mode a) (N/A when there are more than            4 Ack/Nack bits)        -   for TDD using mode b) (time and spatial domain Ack/Nack            bundling)    -   only if UE supports more than 4 Ack/Nack bits, PUCCH format 3-   6) CQI/PMI/RI    -   aperiodic reporting, for any of the N Serving Cells (SCell), as        per channel quality indicator (CQI) request in UL grants    -   periodic reporting, for N Serving Cells, as per radio resource        control (RRC) configuration-   7) one DL-SCH (Downlink Shared Channel) and one hybrid automatic    repeat request (HARQ) entity, for each of the N Serving Cells-   8) HARQ entity initialization/removal at SCell addition/release-   9) Procedures related to SCell activation/deactivation-   10) SCell addition, modification and release    -   with the (non-handover) reconfiguration procedure    -   with the handover procedure-   11) SCell release at RRC connection re-establishment-   12) SCell measurement result inclusion in Measurement Reports-   13) Best non-serving cell reporting in measurement reports-   14) ‘NeedForGaps’ indicaton for each measurement band for each    operating band/band combination-   15) Periodical measurement on SCCs-   16) Measurement reporting trigger Event A1, for SCell-   17) Measurement reporting trigger Event A2, for Scell-   18) Autonomous measurement identity removal-   19) Measurement reporting trigger Event A6-   20) SCell addition within the handover to EUTRA procedure (relevant    if UE supports handover to EUTRA)    In cell aggregation Dario frequency may be needed for a multiple UL    PUSCH. Furthermore, PDSCH decoding may be needed for multiple    composite carriers. Also, more PDCCH search space may be needed.    Optimisation of these requirements by means of the user    categorization can be used to manage the complexity and    implementation cost of a communication device such as a mobile user    equipment.

In the embodiments single frequency cell aggregation can be used toprovide flexibility and benefit to overall system performance. Anexisting carrier aggregation capability set can be modified to allowcoordinated multi-point transmission (CoMP) on a single frequency.Technically, component carriers (CC) can be configured with the samefrequency to allow single frequency cell aggregation as a CoMPtechnique. The carrier aggregation is allowed to have cross-carrierscheduling. Cross cell scheduling can be used for example to transmit aprimary cell downlink from a macro cell and a secondary cell uplink in apico cell.

It is noted that whilst embodiments have been described in relation toLTE-Advanced, similar principles can be applied to any othercommunication system or indeed to further developments with LTE. Also,instead of carriers provided by a base station a carrier comprising maybe provided by a communication device such as a mobile user equipment.For example, this may be the case in application where no fixedequipment provided but a communication system is provided by means of aplurality of user equipment, for example in adhoc networks. Therefore,although certain embodiments were described above by way of example withreference to certain exemplifying architectures for wireless networks,technologies and standards, embodiments may be applied to any othersuitable forms of communication systems than those illustrated anddescribed herein. In some other embodiments the aforementionedembodiments can be adopted for example to orthogonal frequency divisionmultiple access (OFDMA) frequency division duplex (FDD) based mobilecommunication system other than LTE.

The required data processing apparatus and functions of a base stationapparatus, a communication device and any other appropriate apparatusmay be provided by means of one or more data processors. The describedfunctions at each end may be provided by separate processors or by anintegrated processor. The data processors may be of any type suitable tothe local technical environment, and may include one or more of generalpurpose computers, special purpose computers, microprocessors, digitalsignal processors (DSPs), application specific integrated circuits(ASIC), gate level circuits and processors based on multi core processorarchitecture, as non limiting examples. The data processing may bedistributed across several data processing modules. A data processor maybe provided by means of, for example, at least one chip. Appropriatememory capacity can also be provided in the relevant devices. The memoryor memories may be of any type suitable to the local technicalenvironment and may be implemented using any suitable data storagetechnology, such as semiconductor based memory devices, magnetic memorydevices and systems, optical memory devices and systems, fixed memoryand removable memory.

In general, the various embodiments may be implemented in hardware orspecial purpose circuits, software, logic or any combination thereof.Some aspects of the invention may be implemented in hardware, whileother aspects may be implemented in firmware or software which may beexecuted by a controller, microprocessor or other computing device,although the invention is not limited thereto. While various aspects ofthe invention may be illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it is wellunderstood that these blocks, apparatus, systems, techniques or methodsdescribed herein may be implemented in, as non-limiting examples,hardware, software, firmware, special purpose circuits or logic, generalpurpose hardware or controller or other computing devices, or somecombination thereof. The software may be stored on such physical mediaas memory chips, or memory blocks implemented within the processor,magnetic media such as hard disk or floppy disks, and optical media suchas for example DVD and the data variants thereof, CD.

The foregoing description has provided by way of exemplary andnon-limiting examples a full and informative description of theexemplary embodiment of this invention. However, various modificationsand adaptations may become apparent to those skilled in the relevantarts in view of the foregoing description, when read in conjunction withthe accompanying drawings and the appended claims. However, all such andsimilar modifications of the teachings of this invention will still fallwithin the scope of this invention as defined in the appended claims.Indeed there is a further embodiment comprising a combination of one ormore of any of the other embodiments previously discussed.

1. An apparatus for a communication device, the apparatus comprising atleast one processor, and at least one memory including computer programcode, wherein the at least one memory and the computer program code areconfigured, with the at least one processor, to support cell aggregationfor communications with a multiple of cells of a communication systembased on a predefined maximum number of cells on a single carrierresource that can be aggregated by the communication device.
 2. Anapparatus for controlling cell aggregation, the apparatus comprising atleast one processor, and at least one memory including computer programcode, wherein the at least one memory and the computer program code areconfigured, with the at least one processor, to receive from acommunication device information of a predefined maximum number of cellsthe communication device supports for cell aggregation on a singlecarrier resource, and control cell aggregation by the communicationdevice based on the information.
 3. An apparatus according to claim 1,wherein the apparatus is configured to handle signalling of anindication of the maximum number of cells from the communication device.4. An apparatus according to claim 3, wherein the signalling isexplicit.
 5. An apparatus according to claim 3, wherein the signallingis implicit.
 6. An apparatus according to claim 3, wherein theindication is signalled in capability information of the communicationdevice.
 7. An apparatus according to claim 3, wherein the maximum numberof cells is defined by means of a capability information parameter. 8.An apparatus according to claim 1, wherein the communication device isconfigured for simultaneous transmission to and/or reception frommultiple cells on the single carrier resource.
 9. An apparatus accordingto claim 1, wherein the communication device is configured to separatetransmission and/or reception on the single carrier resource based ontime division multiplexing.
 10. An apparatus according to claim 1,wherein the single carrier resource comprises a single frequencycarrier.
 11. An apparatus according to claim 1, wherein the predefinedmaximum number of cells defines the maximum number of physical sharedchannels and/or physical control channels that can be received ortransmitted by the communication device.
 12. An apparatus according toclaim 2, configured to cause monitoring of an identity at a time in asearch space up to the predefined maximum number of cells.
 13. Anapparatus according to claim 1, configured to cause simultaneousmonitoring of a plurality of identities in a search space up to thepredefined maximum number of cells.
 14. An apparatus according to claim1, wherein signalling for controlling cell aggregation by thecommunication device is provided by a controller associated with a cell.15. An apparatus according to claim 1, wherein signalling forcontrolling cell aggregation by the communication device is provided bycontroller apparatus associated with a plurality of cells.
 16. Anapparatus according to claim 1, configured to support the singlefrequency resource communication with multiple cells based on a set ofcapabilities selected from a set of capabilities for communications on amulti-frequency component carrier.
 17. An arrangement comprising a firstcommunication device comprising an apparatus according to claim 1 and atleast one second communication device, wherein the first communicationdevice and the at least one second communication device are configuredto provide cell aggregation on a single frequency resource based ondifferent subsets of capabilities selected from a set of capabilitiesfor aggregated component carrier communication on multiple frequencyresources.
 18. A communication device comprising apparatus in accordancewith claim
 1. 19. A network element comprising an apparatus inaccordance with claim
 2. 20. A method for cell aggregation, comprising:signalling information regarding a predefined maximum number of cellsthat can be aggregated by a communication device on a single carrierresource, and supporting cell aggregation for communications by thecommunication device on the single carrier resource with a multiple ofcells up to said maximum number of cells.
 21. A method for controllingcell aggregation, comprising: receiving information of a predefinedmaximum number of cells a communication device supports for cellaggregation on a single carrier resource, and controlling cellaggregation on the single carrier resource by the communication devicebased on the information.
 22. A method according to claim 20, comprisingcommunicating an indication of the maximum number of cells from thecommunication device to a controller of at least one cell.
 23. A methodaccording to claim 20, wherein signalling of the information of thepredefined maximum number of cells is explicit.
 24. A method accordingto claim 23, comprising signalling a capability information parameterdefining the maximum number of cells.
 25. A method according to claim20, wherein signalling of the information of the predefined maximumnumber of cells is implicit.
 26. A method according to claim 20, whereinthe information of the predefined maximum number of cells is signalledin response to a request for capability information.
 27. A methodaccording to claim 20, comprising simultaneous transmission to and/orreception from multiple cells on the single carrier resource by thecommunication device.
 28. A method according to claim 20, comprisingseparating transmission and/or reception on the single carrier resourcebased on time division multiplexing.
 29. A method according to claim 20,wherein the single carrier resource comprises a single frequencycarrier.
 30. A method according to claim 20, wherein the predefinedmaximum number of cells defines the maximum number of physical sharedchannels and/or physical control channels that can be received ortransmitted by the communication device.
 31. A method according to claim20, comprising monitoring for identities in a search space up to thepredefined maximum number of cells.
 32. A method according to claim 20,wherein signalling for controlling the cell aggregation is provided froma cell or from a plurality of cells depending on the capability categoryof the communication device.
 33. A method according to claim 32,comprising granting by one of the cells a physical downlink sharedchannel provided by any of the multiple of cells.
 34. A method accordingto claim 20, comprising supporting single frequency resourcecommunication with a multiple of cells based on a set of capabilitiesselected from a set of capabilities for communications on amulti-frequency component carrier.
 35. A method according to claim 20,wherein downlink assignments are provided either with or without a cellindicator depending on the capability category of the communicationdevice.
 36. A method according to claim 20, comprising controlling poweron a serving cell basis.
 37. A method for communications on a systemwhere cell aggregation is available, comprising: providing singlefrequency resource aggregation for communications by a firstcommunication device configured with a subset of capabilities selectedfrom a set of capabilities defined for a communication device capable ofcomponent carrier communication on multiple frequency resources, andproviding single frequency resource aggregation for communications by atleast one second communication device configured with a different subsetof capabilities selected from said set of capabilities defined for acommunication device capable of component carrier communication onmultiple frequency resources.
 38. A computer program comprising codemeans adapted to perform the steps of claim 20 when the program is runon a processor.